.container{
    display:grid;
    grid-template-rows: 30px 1fr 1fr;
    grid-template-columns: 1fr 1fr 1fr;
    grid-template-areas:
    "navbar navbar navbar"
    "sidebar content content"
    "sidebar content content";
    grid-row-gap: 10px;
    grid-column-gap: 5px;
    width: 300px;
    height: 300px;
    border: 1px solid;
}

.item{
    border: 1px solid red;
}

.item:nth-child(1){
    grid-area: navbar;
}


.item:nth-child(2){
    grid-area: sidebar;
}

.item:nth-child(3){
    grid-area: content;
}